This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The following program proposal narrative describes individual experiments for several projects that involve the use of synchrotron radiation for structure determination using x-ray diffraction methods to address problems concerning the mechanism of enzyme catalyzed reactions. Toward these ends, we are determining the structure of novel enzymes and utilizing information obtained by previous biochemical and biophysical studies as a basis for capturing and determining the structure of enzymes in defined states that mimic intermediates along the pathway of catalysis. The overall goal of these studies is to utilize the structures of defined states of certain enzymes to contribute to the overall understanding of enzyme mechanism and therefore there is significant value in conducting these studies at high resolution. We are currently pursuing these studies for enzymes involved in hydrogen production, nitrogen reduction, phosphate ester hydrolysis, and bioconversion of alkenes and ketones.